Cellular Transport

1. Cellular Transport

2. About Cell Membranes • All cells have a cell membrane. Outer most living part of a cell! • Functions: • Controls what enters and exits the cell to maintain an internal balance called homeostasis • Provides protection and support for the cell TEM picture of a real cell membrane.

3. About Cell Membranes (continued) • 4. Cell membranes have pores (holes) in it • Selectively permeable: Allows some molecules in and keeps other molecules out • The structure helps it be selective! Pores

4. About Cell Membranes Con’t • What would a cell want to enter? • What would a cell want to leave?

5. About Cell Membranes (continued) • Membranes are like tea bags or like a screened window. Small particles pass more freely than large ones. • Ions do not pass as easily as uncharged particles do. • Different kinds of cell are permeable to different substances

6. About Cell Membranes (continued) • Structure of cell membrane Lipid Bilayer -2 layers of phospholipids • Phosphate head is polar (water loving) • Fatty acid tails non-polar(water fearing) • Proteins embedded in membrane Phospholipid Lipid Bilayer

7. Fluid Mosaic Model of the cell membrane Polar heads love water & dissolve. Membrane movement animation Non-polar tails hide from water. Carbohydrate cell markers Proteins

8. Structure of the Cell Membrane Carbohydrate chains Proteins Transport Protein Animations of membrane structure Phospholipids Go to Section:

9. Structure of the Cell Membrane • Membrane proteins- • Regulate what molecules can pass across the membrane • Serve as enzymes and take part in chemical reactions. • Act as markers for cell • and molecular • recognition. • ●Cell surface receptors

10. Weeee!!! high low This is gonna be hard work!! high low Types of Cellular Transport • Passive Transport cell doesn’t use energy • Diffusion • Facilitated Diffusion • Osmosis • Active Transport cell does use energy • Protein Pumps • Endocytosis • Exocytosis

11. Passive Transport • cell uses no energy • molecules move randomly • Molecules spread out from an area of high concentration to an area of low concentration. • (HighLow) • Only occurs if there is a concentration gradient • Three types:

12. 3 Types of Passive Transport • Diffusion Ex. O2, CO2, lipids • Facilitative Diffusion – diffusion with the help of transport proteins. Ex.- Glucose • Osmosis – diffusion of water

13. Simple Diffusion Animation Passive Transport:1. Diffusion • Diffusion: random movement of particles from an area of high concentration to an area of low concentration. (High to Low) • Diffusion continues until all molecules are evenly spaced (dynamic equilibriumis reached)-Note: molecules will still move around but stay spread out. http://bio.winona.edu/berg/Free.htm

14. Passive Transport: 2. Facilitated Diffusion A B 2. Facilitated diffusion: diffusion of specific particles through transport proteins found in the membrane • Transport Proteins are specific – they “select” only certain molecules to cross the membrane • Transports larger or charged molecules Facilitated diffusion(Channel Protein) Diffusion (Lipid Bilayer) Carrier Protein • http://bio.winona.edu/berg/Free.htm

15. Passive Transport: 2. Facilitated Diffusion Glucose molecules Cellular Transport From a- High High Concentration Cell Membrane Protein channel Low Concentration Low Transport Protein Through a  Go to Section:

16. Passive Transport: 3. Osmosis Osmosis animation • 3.Osmosis:diffusion of water through a selectively permeable membrane • Water moves from high to low concentrations • Water moves freely through pores. • Solute (green) too large to move across.

17. Effects of Osmosis on Life • Osmosis- diffusion of water through a selectively permeable membrane • Water is so small and there is so much of it the cell can’t control it’s movement through the cell membrane.

18. Hypotonic Solution Hypotonic: The solution has a lower concentration of solutes and a higher concentration of water than inside the cell. (Low solute; High water) Result: Water moves from the solution to inside the cell): Cell Swells and bursts open (cytolysis)!

19. Hypertonic Solution Hypertonic: The solution has a higher concentration of solutes and a lower concentration of water than inside the cell. (High solute; Low water) shrinks Result: Water moves from inside the cell into the solution: Cell shrinks (Plasmolysis)!

20. Isotonic Solution Isotonic: The concentration of solutes in the solution is equal to the concentration of solutes inside the cell. Result: Water moves equally in both directions and the cell remains same size! (Dynamic Equilibrium)

21. What type of solution are these cells in? B C A Hypertonic Isotonic Hypotonic

22. How Organisms Deal with Osmotic Pressure • Bacteria and plants have cell walls that prevent them from over-expanding. In plants the pressure exerted on the cell wall is called turgor pressure. • A protist like paramecium has contractile vacuoles that collect water flowing in and pump it out to prevent them from over-expanding. • Salt water fish pump salt out of their specialized gills so they do not dehydrate. • Animal cells are bathed in blood. Kidneys keep the blood isotonic by remove excess salt and water. • Paramecium (protist) removing excess water video

23. Cell Wall Structure • Outer most, dead, found in plant, bacteria, fungi and protists, though the structure can vary. Functions to keep cell shape.

24. Active Transport • cell uses energy • actively moves molecules to where they are needed • Movement from an area of low concentration to an area of high concentration • (Low  High) • Three Types:

25. Sodium Potassium Pumps (Active Transport using proteins) Types of Active Transport 1. Protein Pumps -transport proteins that require energy to do work • Example: Sodium / Potassium Pumps are important in nerve responses. Protein changes shape to move molecules: this requires energy (ATP)!

26. Types of Active Transport • 2. Endocytosis: taking bulky material into a cell • Uses energy • Cell membrane in-folds around food particle • Phagocytosis-“cell eating” • forms food vacuole & digests food • This is how white blood cells eat bacteria! • Pinocytosis- “cell drinking” This is how an egg cell gets it nutrients.

27. Types of Active Transport Endocytosis & Exocytosis animations 3. Exocytosis:Forces material out of cell in bulk • membrane surrounding the material fuses with cell membrane • Cell changes shape – requires energy • EX: Hormones or wastes released from cell